Hornsea Project Three Offshore Wind Farm · 2019. 3. 27. · Checked by Karma Leyland Approved by...
Transcript of Hornsea Project Three Offshore Wind Farm · 2019. 3. 27. · Checked by Karma Leyland Approved by...
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Hornsea Project Three Offshore Wind Farm
Hornsea Project Three
Offshore Wind Farm
Appendix 26 to Deadline 9 submission - Safety Justification for Single Line of Orientation Layout
Date: 26th March 2019
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Document Control
Document Properties
Organisation Ørsted Hornsea Project Three
Author Anatec
Checked by Karma Leyland
Approved by Andrew Guyton
Title Safety Justification for Single Line of Orientation Layout
PINS Document Number
n/a
Version History
Date Version Status Description / Changes
18.03.2019 A Draft Compilation of NRA and Examination Submissions Supporting a Single Line of Orientation.
26/03/2019 B FINAL Compilation of NRA and Examination Submissions Supporting a Single Line of Orientation submitted at Deadline 9
Ørsted
5 Howick Place,
London, SW1P 1WG
© Orsted Power (UK) Ltd, 2019. All rights reserved
Front cover picture: Kite surfer near a UK offshore wind farm © Ørsted Hornsea Project Three (UK) Ltd., 2019.
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Table of Contents
1. Introduction ................................................................................................................................................. 1
Background ..................................................................................................................................................... 1
Purpose of this Report .................................................................................................................................... 1
2. Project Details ............................................................................................................................................ 1
3. Guidance .................................................................................................................................................... 3
4. Consultation ............................................................................................................................................... 3
Maritime and Coastguard Agency ................................................................................................................... 3
Trinity House ................................................................................................................................................... 4
Cruising Association ....................................................................................................................................... 4
Royal Yachting Association ............................................................................................................................ 4
Regular Operators .......................................................................................................................................... 5
5. Vessel Traffic .............................................................................................................................................. 6
Data Overview ................................................................................................................................................ 6
Traffic Density at Hornsea Developments ....................................................................................................... 9
Anchoring Activity within Array Area ............................................................................................................. 10
Traffic Behaviour Internally within Existing Arrays ........................................................................................ 10
6. Search and Rescue .................................................................................................................................. 12
Mark Prior Bio ............................................................................................................................................... 13
Search and Rescue Access Lanes ............................................................................................................... 13
Lack of Precedent ......................................................................................................................................... 13
Turning Within the Array ............................................................................................................................... 13
Minimum Spacing ......................................................................................................................................... 15
7. Historical Incidents ................................................................................................................................... 15
8. Other Evidence ......................................................................................................................................... 20
Mitigation Measures – Pre Submission ......................................................................................................... 20
Mitigation Measures – Post Submission ....................................................................................................... 21
SOLAS Obligations ....................................................................................................................................... 22
Hornsea Three as a Standalone Development ............................................................................................. 22
Internal Allision Risk Impact from Navigational Risk Assessment ................................................................. 23
9. Other Constraints ..................................................................................................................................... 31
10. Summary and Conclusion ........................................................................................................................ 32
11. References ............................................................................................................................................... 34
List of Tables
Table 2.1 Key project parameters ................................................................................................................ 2 Table 5.1: Traffic density within each Hornsea development array area ....................................................... 9
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Table 6.1: EASA Part SERA recommended speeds ................................................................................... 14 Table 6.2 Minimum spacing at UK offshore wind farm developments ........................................................ 15 Table 6.3: Summary of historical collision and allision incidents involving wind farm sites ......................... 18 Table 7.1: Effects associated with navigation internally within the Hornsea Three array area .................... 29
List of Figures
Figure 2.1 Overview of NRA layout ............................................................................................................... 2 Figure 5.1 Overview of vessel traffic data within 10 nm of Hornsea Three array area (40 days summer and
winter 2016) ................................................................................................................................. 7 Figure 5.2 Recreational vessels within 10 nm of Hornsea Three array area (40 days summer and winter) .. 8
Figure 5.3 Fishing vessels within 10 nm of Hornsea Three array area (40 days summer and winter) .......... 9 Figure 5.4: AIS recreational vessels within London Array site boundary (Mar 2016 to Feb 2017) ............... 11 Figure 5.5: AIS fishing vessels within London Array site boundary (Mar 2016 to Feb 2017) ........................ 12 Figure 6.1 Historical SAR incidents within 10 nm of Hornsea Three array area .......................................... 16 Figure 6.2 MAIB incident locations by incident type within 10 nm of Hornsea Three array area ................. 17 Figure 6.3 RNLI incident locations by incident type within 10 nm of Hornsea Three array area .................. 18 Figure 7.1: GMDSS sea areas ..................................................................................................................... 24
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1. Introduction
Background
Guidance provided in the Maritime and Coastguard Agency’s (MCA) Marine Guidance Note
(MGN) 543 states ‘Developers should plan for at least two lines of orientation unless they can
clearly demonstrate that fewer is acceptable’. Using this guidance as a basis, the Applicant has
been assessing layouts and layout strategies for over two years as part of the Environmental
Impact Assessment (EIA) process. Following the Preliminary Environmental Impact Assessment
(PEIR) and responses received as part of the Section 42 consultation, the Applicant moved, in
consultation with the MCA and Trinity House (TH), to firstly develop a set of Layout Development
Principles to provide a framework for post consent layout approval and secondly to base the
Navigational Risk Assessment (NRA) and the Environmental Statement on a layout with a single
line of orientation (SLoO).
As reflected at Deadline 4 responses, as part of the Hornsea Three Examination phase both the
MCA and TH agreed that a single line of orientation would be acceptable if a suitable safety
justification was presented and agreed. The Applicant clarified that its safety justification was
presented in the Navigational Risk Assessment (NRA) dated May 2018, as supplemented with
information requested by the MCA and TH during the examination. At the Issue Specific Hearing
(ISH) on the 7th March 2019 submissions made by TH indicated that it would be helpful to have the
safety justification in one document. In response the Applicant agreed to represent the work
undertaken as part of the NRA and also the technical submissions into the examination process
from the Search and Rescue (SAR) Helicopter Specialist into one document comprising the safety
justification for a SLoO. This document serves that purpose and demonstrates how fewer than two
lines of orientation is ’acceptable’ (as defined in accordance with MGN 543) for Hornsea Three.
Purpose of this Report
This report serves as the safety justification which the MCA have requested in line with Principle 3
of the Layout Development Principles. The report shows that a SLoO incorporated into the
Hornsea Three array layout is ’acceptable and safe’ (as defined in accordance with MGN 543) by
summarising relevant information given in Volume 5, Annex 7.1: Navigational Risk Assessment of
the Environmental Statement (hereafter referred to as the “NRA”) and materials produced since
the NRA was submitted as part of the examination process.
2. Project Details
The layout considered in the NRA is shown in Figure 2.1. The symbology used in Figure 2.1 for
turbine locations has been designed to give a clearer idea of the size of the turbines in relation to
the Hornsea Three array area as a whole.
The layout consisted of the following 319 structures:
• 300 turbines;
• 12 offshore High Voltage Alternating Current (HVAC) transformer substations;
• Four offshore High Voltage Direct Current (HVDC) converter substations; and
• Three accommodation platforms.
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The minimum structure spacing in the NRA layout is 1,000 m. Key project parameters provided in
the NRA are summarised in Table 2.1.
Figure 2.1 Overview of NRA layout
Table 2.1 Key project parameters
Parameter Updated Application Value
Maximum number of turbines 300
Maximum number of other structures 19 (see above for breakdown)
Maximum blade tip height (above Lowest Astronomical Tide (LAT))
250 m
Maximum hub height (above LAT) 153 m
Maximum rotor diameter 195 m
Minimum spacing 1,000 m
Minimum blade clearance (above LAT) 34.97 m
Worst case foundation for shipping and navigation Jacket
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3. Guidance
Section 2 of the NRA outlines the guidance and legislation used to inform the assessment. This
includes MGN 543 which, as noted in Section 1, advises that a SLoO layout will be agreed if
demonstrated to be acceptable. However, there are no parameters within the guidance to identify
what is acceptable and so this has been assumed based on both early consultation and the MCA’s
remit that the developer must demonstrate that the risk is As Low As Reasonably Practicable
(ALARP) in line with the MCAs own methodologies1 which the MCA require to be a template when
preparing NRAs. For clarity this methodology has been used for the NRA for Hornsea Three.
Although not referenced by either guidance document, the MCA have recently noted during
examination that geotechnical constraints may be used to aid the justification for a SLoO, i.e.
demonstrating that it is not physically possible to apply two lines of orientation2.
As demonstrated in section 4, this safety justification has been built upon the safety of both surface
craft and SAR aircraft and is therefore in accordance with MGN 543.
4. Consultation
Throughout the consenting process for Hornsea Three consultation has been undertaken with
relevant shipping and navigation stakeholders including the MCA. This section provides detail of
consultation undertaken relevant to the topic of the array layout, including consultation summarised
in the NRA.
Maritime and Coastguard Agency
During a consultation meeting in February 2017, both the MCA and Trinity House (TH) were clear
that MGN 543 states that developers should plan for two lines of orientation in the Hornsea Three
array layout unless they can clearly demonstrate that fewer is acceptable and safe for SAR
helicopter operations. In consultation with the MCA, the Applicant subsequently took the decision
to progress the final NRA based upon a SLoO layout.
During a consultation meeting in December 2017, the key points of the safety justification for a
SLoO were discussed. These key points are listed below alongside where they are addressed in
greater detail within this report.
• Agreement between Hornsea Three and the MCA that vessel traffic levels were low within the
array area (section 5 – traffic density at Hornsea developments);
• Fishing stakeholders are more concerned with minimum spacing and foundation types than
array layout (section 4 – regular operators);
1 Methodology for Assessing the Marine Navigational Safety Risk & Emergency Response Risks of Offshore Renewable Energy Installations (OREI) (MCA, 2016). 2 MCA’s Responses to the Examining Authority’s request for further information (Rule 17) (REP7-102)
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• Hornsea Three resources will be on site and most likely to respond to an incident (section 8 –
International Convention for the Safety of Life at Sea (SOLAS) obligations); and
• No other project borders the Hornsea Three array area (section 8 – Hornsea Three as a
standalone development).
Trinity House
During a consultation meeting in December 2017, TH viewed the change to a SLoO as “a positive
step forward” compared to the irregular layout assessed in the Preliminary Environmental
Information Report (PEIR) and did not express a need for further refinement to two lines of
orientation. At this meeting TH agreed that commercial vessels will not navigate within the array.
The Applicant noted their commitment to a SLoO and added that a safety justification supporting a
SLoO would be included within the NRA.
Cruising Association
During consultation the Cruising Association (CA) has stated that they have no major issues with
the development of Hornsea Three and noted that many yachtsman will choose not to transit
through an offshore wind farm. Furthermore, the CA felt that the additional time and distance
incurred as a result of avoiding the array would mostly be minimal and it is likely that yachts and
recreational craft may at the time of passage choose to avoid or be in a position where they should
avoid the array.
The CA commented that Hornsea Three is located in an area of very light yachting and
recreational traffic. This is in agreement with the vessel traffic data assessed in the NRA which
provides very low numbers of recreational vessel movements. Although “straight see-through
channels between the turbines” are preferable, the CA confirmed that any disadvantage for not
doing so “may prove minimal and therefore acceptable to many”.
In their Section 42 response the CA noted that the layout of structures should be in straight lines
following a rectangular or similar pattern, although their view was eased by the adoption of a
minimum spacing of 1,000 metres (m) or greater. Any consequent disorientation of helmsman can
be mitigated to an extent by additional marking and lighting. As per the NRA, structures in the
array will be marked and lit in accordance with IALA Recommendation O-139 on The Marking of
Man-Made Offshore Structures (IALA, 2013) and TH and the MCA will be consulted in relation to
the need for additional internal aids to navigation.
In the SoCG between Hornsea Three and the CA the CA agree that Hornsea Three has minimal
impacts on recreational craft and are therefore in agreement with the Layout Development
Principles approach being developed in conjunction with the MCA and TH.
Royal Yachting Association
During consultation the Royal Yachting Association (RYA) expressed no concerns given that the
level of recreational activity at the distance offshore of the Hornsea Three array area is very low.
The RYA added that at the distance offshore any recreational user would be very experienced and
well-equipped. It is noted that the RYA had no concerns with the indicative layouts which were
presented at the PEIR stage. The PEIR layouts included no lines of orientation (irregular).
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The RYA were provided but had no comments with regard to the Environmental Statement and
NRA.
Regular Operators
Regular operators were identified in the NRA using the Automatic Identification System (AIS) traffic
data and were invited to comment on the development and attend a Hazard Workshop held at the
Ørsted offices in London in February 2017.
Regular operators whose representatives attended the Hazard Workshop included the following:
• DFDS Seaways;
• Aggregate Industries UK;
• DEME Building Materials;
• Centrica (now Spirit Energy);
• Vroon Offshore Services; and
• Dutch Fishing Association VISNED.
It is also noted that a representative from the MCA was present at the Hazard Workshop.
During the meeting, all commercial operators present agreed that commercial vessels (non-fishing)
would not use the array area for transiting. Specifically, both DFDS Seaways and marine
aggregate dredger representatives confirmed that the array layout is a non-issue since their
vessels would not enter the array area. Oil & Gas representatives stated that their support vessels
would choose to use the navigational corridor between the Hornsea developments rather than
transit through the array area, noting that this would not significantly increase routeing distances.
Although not in attendance at the Hazard Workshop, commercial ferry operator KESS expressed
similar views, noting a slight impact on routeing but that vessels can avoid the area and therefore
there are no notable safety concerns.
VISNED noted that fishing activity would be possible within the indicative layout presented at the
PEIR stage (an irregular layout with no lines of orientation) and commented that “for fishing, the
separation between turbines is more important than the regularity of the layout”. Demersal trawlers
active within the array are expected to target specific fishing grounds meaning that it is unlikely that
the skippers would choose to fish along a fixed line of orientation in the array layout.
VISNED also noted that in good weather fishing vessel are likely to transit through the array. It is
noted that Dutch fishing vessels (represented by VISNED) are predominant in the area.
Regular operator consultation clearly indicates that, with the exception of fishing vessels,
commercial traffic would be unlikely to transit through the array and therefore there is no, or
minimal, additional benefit to safe surface navigation by including two lines of orientation in the
array layout. In the case of fishing vessels the NRA remarks that the majority of risk associated
with internal navigation is related to vessels engaged in fishing rather than transiting.
In summary, it is clear that no consultee expressed concerns from a safety perspective or
otherwise in relation to a SLoO.
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5. Vessel Traffic
Data Overview
The NRA included a baseline navigation review of the Hornsea Three array area using marine
traffic data. The dataset analysed consisted of a combined dataset of 40 days of AIS, visual and
Radar data recorded within 10 nautical miles (nm) of the array area (the “study area”) from survey
vessels working at the Hornsea Three array area during summer (26 days) and winter (14 days)
2016. This data satisfied MCA requirements as set out in MGN 543 and was approved by the MCA
in April 2017.
All Vessels
Plots of the vessel tracks recorded during each survey period, colour-coded by vessel type, and
excluding temporary traffic (such as the survey vessels and traffic associated with temporary
drilling rigs) is presented in Figure 5.1 (Panels A and B). Figure 5.1 also presents the
corresponding density grid for each survey period (Panels C and D).
For the 26 days analysed in summer 2016, there was an average of 42 unique vessels per day
passing within the study area. In terms of vessels intersecting the Hornsea Three array area, there
was an average of 15 unique vessels per day. The majority of tracks were cargo vessels (33% of
traffic within the Hornsea Three array area) and fishing vessels (30%).
For the 14 days analysed in winter 2016, there was an average of 28 unique vessels per day
passing within the Hornsea Three array area study area. In terms of vessels intersecting the
Hornsea Three array area, there was an average of 13 unique vessels per day. The majority of
tracks were cargo vessels (45% of traffic within the Hornsea Three array area) and tankers (21%).
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Figure 5.1 Overview of vessel traffic data within 10 nm of Hornsea Three array area (40 days summer and winter 2016)
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Recreational Vessels
A plot of the recreational vessel tracks recorded throughout the survey period is presented in
Figure 5.2. It is noted that 45% of all recreational activity was recorded over a period of two days
when an annual sailing race passed through the Hornsea Three array area.
Figure 5.2 Recreational vessels within 10 nm of Hornsea Three array area (40 days summer and winter)
Fishing Vessels
A plot of the fishing vessel tracks recorded throughout the survey period is presented in Figure 5.3.
It can be seen that fishing vessels were tracked transiting through the Hornsea Three array area
as well as actively engaged in fishing activity.
Fishing vessel sightings (over flight and/or vessel-based) and satellite data (from the MMO) was
used to validate the AIS, visual and Radar dataset and showed good correlation.
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Figure 5.3 Fishing vessels within 10 nm of Hornsea Three array area (40 days summer and winter)
Traffic Density at Hornsea Developments
Table 5.1 summarises the density of vessel traffic recorded on AIS, visual and Radar during the
NRA surveys undertaken for each Hornsea development, noting that the data for each NRA was
approved by the MCA.
Table 5.1: Traffic density within each Hornsea development array area
Development
Surface Area
of Array Area
(nm2)
Average Unique Vessels per Day Within Array Area
Traffic Density (Daily Vessels
per nm2) Summer Winter All
Hornsea Project One
118 12 13 12 0.10
Hornsea Project Two
134 12 12 12 0.09
Hornsea Three 202 15 13 14 0.07
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It can be seen that the levels of vessel traffic for each Hornsea development was similar with
Hornsea Three giving the highest average number of unique vessels per day by a small margin.
However, when accounting for the significantly greater surface area covered by the Hornsea Three
array area (71% greater than Hornsea Project One and 51% greater than Hornsea Project Two),
the vessel density is lower at Hornsea Three than at the other Hornsea developments.
Moreover, it is noted that the AIS data used for Hornsea Three was collected in 2016 at which
point all fishing vessels of length greater than 15 m were required to carry AIS equipment as per
Annex II of European Union (EU) Directive 2002/59/EC. This compares with length thresholds of
45 m and 24 m at the time of data collection for Hornsea Project One (2011) and Hornsea Project
Two (2012), respectively. Therefore, given the significant presence of fishing vessels in all three
Hornsea developments, in reality the traffic density for Hornsea Project One and Hornsea Project
Two may be significantly higher than that of Hornsea Three.
With increasing experience and knowledge of navigation by SAR assets within offshore wind
farms, the Applicant understands that precedence should not be set with respect to the number of
lines of orientation in a layout. However, both Hornsea Project One and Hornsea Project Two had
layouts approved by the MMO in consultation with the MCA with a SLoO (noting vessel density
being greater than that of Hornsea Three). Therefore, from the perspective of local vessel traffic
and impacts on surface navigation, it is considered reasonable for Hornsea Three to also be
consented with a SLoO.
Anchoring Activity within Array Area
As part of the vessel analysis undertaken in the NRA, an assessment was undertaken to identify
anchoring activity within a 10 nm buffer of the Hornsea Three array area. Considering both vessels
broadcasting an “at anchor” status and vessels travelling at speeds of less than one knot (kt) for
more than 30 minutes no vessels were deemed to be at anchor. This may be attributed to the
distance offshore and the moderate water depth.
This finding adds further weight to the information provided in the previous section that vessel
activity within the Hornsea Three array area is relatively low.
Traffic Behaviour Internally within Existing Arrays
London Array Offshore Wind Farm has been fully operational since 2013 and was consented
within a busy and seasonal area for small craft. A specific buoyed navigation channel (Fouglars
Gat) was designed in the position of an existing preferred route, although does not form part of
either of the primary lines of orientation in the array layout. The minimum turbine spacing at
London Array is approximately 650 m.
As part of the Hornsea Three NRA, a year of AIS data, collected between March 2016 and
February 2017, was analysed within the London Array site boundary in order to gain an
understanding of the behaviour of vessel traffic transiting internally within an array.
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Figure 5.4 presents the recreational vessel tracks recorded within the London Array site boundary.
During the one-year period 140 unique recreational transits were recorded, all but eight tracks
transited through Foulgers Gat for the majority of their transit; these vessels generally made
passage in straight lines using the buoyed navigation channel. Of those eight tracks which did not
fully stay within Foulgers Gat, passage was not necessarily in straight lines, and was not dictated
by the available lines of orientation.
Figure 5.4: AIS recreational vessels within London Array site boundary (Mar 2016 to Feb 2017)
Figure 5.5 presents the fishing vessel tracks recorded within the London Array site boundary. Only
32 unique fishing vessel transits were recorded. Of the 49 tracks recorded, 23 broadcast a
navigational status of “engaged in fishing”, with these near the southern boundary; the remaining
26 tracks consisted of passages through the array, with vessels not, in the majority, following the
main lines of orientation. This is reflective of comments from fishing representatives during
consultation, as noted in section 4.
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This technical evidence provides useful context re the MCA’s assertion that the safest way to
navigate through an offshore wind farm is when multiple lines of orientation are in place (see MCA
consultation in section 2), with vessels at London Array opting to take alternative routes which are
not necessarily confined to the available lines of orientation. Moreover, evidence suggests that
larger commercial vessels are not likely to navigate through an offshore wind farm; this is
evidenced by extensive traffic surveys and has been reiterated by commercial operators over
many years during consultation for many developments. As noted in section 4 (Regular
Operators), this is also the case for Hornsea Three, with large commercial operators in the area
such as DFDS Seaways making clear during consultation that they would not make passage
through the array.
Figure 5.5: AIS fishing vessels within London Array site boundary (Mar 2016 to Feb 2017)
6. Search and Rescue
Extensive technical assessment has been undertaken on the impact of Hornsea Three on the
ability of SAR helicopters to undertake operations within the array area, led by Mark Prior, SAR
Helicopter Specialist. Appendix 14 to the Applicant’s Deadline 2 submission provides an in-depth
analysis of the impact the development may have on SAR accessibility; some of the key points
raised are outlined in the following subsections.
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Mark Prior Bio
Mark Prior is a highly experienced aviation professional with a wide range of expertise in
certification, safety analysis, investigation, operations, technical issues and regulations. Over 38
years’ experience as a pilot, initially in the Royal Air Force (RAF), then as a licensed civil pilot with
concurrently 25 years of experience as an Experimental Test Pilot. Since 2003 mark has been an
industry representative on a number of rule-making, operational and research groups.
Search and Rescue Access Lanes
From Annex 5 to MGN 543, a SAR access lane is an area within which “there shall be no OREIs,
or other structures, in the wind farm or on the boundary that present an obstacle or risk to SAR
helicopters flying along”. The purpose of a SAR access lane is to ensure that “a SAR helicopter
can fly from one side of a wind farm to the other”. Furthermore, “the lanes also provide safer and
more predictable paths through a wind farm for surface rescue vessels”.
Lack of Precedent
No current experience exists with SAR aviation operations in UK offshore wind farm, with only
trials undertaken to date which have not incorporated Round 3 offshore wind farms, with the
exception of at Rampion Offshore Wind Farm (3.6 MW turbines in a grid layout). In particular, there
is no experience of conducting a search in an array where the turbines are spaced at least
one kilometre (km) apart and current Standard Operating Procedures (SOP) are based on more
tightly packed arrays, which will be of limited validity for Hornsea Three. However, the MCA have
conducted flights with spacing around 800 to 900 m to explore SAR issues.
In some ways a parallel can be drawn to searching in hilly terrain where the helicopter can be
constrained to valleys when the hill tops are covered in cloud. Unlike hilly terrain, all obstacles in a
turbine array will be controlled, accurately mapped and information provided to the crew by paper
and electronic means. The MCA, and their helicopter contractor, are able to modify their search
profiles and procedures to take account of the obstacle environment presented in Round 3
offshore wind farm arrays.
Turning Within the Array
The MCA provided data to the Applicant from a trial conducted by their SAR helicopter contractor
over Loch Ness in Scotland during the summer of 2018. Conducting such trials is problematic and
can require the use of specialist tracking equipment in order to produce accurate and repeatable
results. The Applicant raised a concern that the single image provided by the MCA appeared to
show turns at an inconsistent angle of bank as the orbits were not round, despite it being stated
that the turns were flown in zero wind. Furthermore, it did not appear to show the diameter being
measured accurately.
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The MCA later provided two diagrams showing turning performance. The first showed a turn into a
40 kt wind with the wind 30 degrees (°) to the right of track. The radius of turn for a 180° turn of
0.12 nm coincides with the Applicant’s calculations. A second diagram with the 40 kt wind at 90° to
the right showed a reduced turning radius for a 180° turn of 0.1 nm. These diagrams support the
Applicant’s calculations of turning circle. The Applicant used weather data from the J6A platform
and seven years’ worth of met data from the Hornsea Project One array area to confirm that
simultaneous occurrences of poor visibility and strong winds were extremely uncommon. The J6A
met data for one year had no occurrences of visibility below 1000 m and wind speed above 30 kt,
whilst the Hornsea Project One data, recorded at 10 minute intervals for seven years, had a
probability of 0.0166% of strong winds and poor visibility occurring concurrently.
The European Aviation Safety Agency (EASA) Part Standardised European Rules of the Air
(SERA) is used for guidance as to the speeds flown against visibility. Although an advisory
airspeed is provided, this is really the ground speed, as that determines the closure rate with
obstacles. Table 6.1 gives the recommended speeds for differing levels of visibility.
Table 6.1: EASA Part SERA recommended speeds
Visibility (m) Advisory speed (kt) Time to cover “visible distance” at “advisory speed” (seconds)
800 50 31
1,500 100 29
2,000 120 32
With visibility in excess of 1,000 m, the turbine ahead, and laterally, will be visible and so a turn
can be made without risk of colliding with the turbine. With visibility below 1,000 m, the airspeed
will be reduced towards 50 kt, requiring a smaller distance to turn.
The MCA have suggested that a turn would likely be undertaken with an angle of bank of 20 to
30°, with the greatest speed applied 80 kt (where visibility is good). The MCA have also suggested
that 1 nm is required to allow sufficient space to turn an aircraft, particularly in poor weather.
Classic aerodynamic theory shows that:
𝑟 =𝑣2
𝑔 tan ∅
Where:
𝑟 = 𝑟𝑎𝑑𝑖𝑢𝑠 𝑜𝑓 𝑡𝑢𝑟𝑛 (𝑚)
𝑔 = 9.81𝑚/𝑠2
𝑣 = 𝑡𝑟𝑢𝑒 𝑎𝑖𝑟𝑠𝑝𝑒𝑒𝑑 (𝑘𝑡)
∅ = 𝑎𝑛𝑔𝑙𝑒 𝑜𝑓 𝑏𝑎𝑛𝑘 (°)
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Applying this to a turn at 80 kt with angle of bank 20°, the radius of turn would be approximately
0.25 nm (diameter 0.50 nm). In poor visibility the airspeed would be reduced, and thus the radius
of turn would also be reduced. The MCA and Applicant have different positions on whether a
Helicopter Refuge Area is essential. However, agreement reached on Principle 5 does provide for
a Helicopter Refuge Area whose exact dimensions will be determined post consent.
Minimum Spacing
Table 6.2 presents the minimum spacing at a number of operational or under construction offshore
wind farms in the UK. Values are based on distances obtained from United Kingdom Hydrographic
Office (UKHO) Admiralty charts.
Table 6.2 Minimum spacing at UK offshore wind farm developments
Development Minimum Turbine Spacing
within NRA (m) Increase in Minimum Turbine
Spacing at Hornsea Three
Hornsea Project One 878 13.9%
Hornsea Project Two 924 8.23%
East Anglia One 675 48.2%
East Anglia Three 675 48.2%
Rampion 600 66.7%
London Array (Round 2 development) 650 53.9%
The minimum spacing between turbines for Hornsea Three of 1,000 m is greater and in some
cases significantly greater than other offshore wind farms in the UK. The two other Hornsea
developments are the only cases where the minimum spacing is somewhat similar and layouts for
these developments have a SLoO.
The greater minimum spacing gives vessels more sea room to navigate and manoeuvre within the
Hornsea Three array area (including turning circles and rates of turn).
Given the distance offshore and the presence of project vessels for Hornsea Three the likelihood
of a SAR operation in which a widespread search is required is very low. Helicopter Refuge Areas
are intended to support access to, and within, the array area, including in the instance that a
medical evacuation is required.
7. Historical Incidents
The NRA considers SAR operations data within the Hornsea Three array area study area and
found that in the five-year period between 2011 and 2015 a total of nine SAR operations were
recorded, as shown in Figure 7.1.
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Figure 7.1 Historical SAR incidents within 10 nm of Hornsea Three array area
Only one of these SAR operations was recorded within the Hornsea Three array area and all the
incidents involved a medical rescue conducted in the daytime without the need for a search. From
this data it is evident that the region within the southern North Sea where Hornsea Three is to be
located does not endure a high level of marine incidents which require SAR operations. This will be
furthered by the presence of Hornsea Three since project vessels will be fully certified and very
likely able to render assistance under SOLAS obligations in addition to a SAR Asset (see section 8
– SOLAS Obligations), and in the case of less protracted incidents may be able to provide a
sufficient response without the need for a SAR Asset. Further discussions will take place with the
MCA post consent as part of the ERCoP on emergency response requirements.
In addition to incidents involving SAR operations, the NRA also analysed incident data provided by
the Maritime Accident Investigation Branch (MAIB) and Royal National Lifeboat Institution (RNLI)
during the 10-year period between 2005 and 2014.
Figure 7.2 presents the locations of accidents, injuries and hazardous incidents reported to the
MAIB within the various study areas considered in the NRA relating to shipping and navigation.
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Figure 7.2 MAIB incident locations by incident type within 10 nm of Hornsea Three array area
A total of five unique incidents, with one incident involving two vessels, were reported within the
Hornsea Three array area study area, corresponding to an average of one incident every two
years. None of these incidents occurred within the Hornsea Three array area. “Accident to Person”
was the most frequent incident type and Oil & Gas affiliated vessels were the most frequent
casualty type.3
Figure 7.3 presents the locations of incidents responded to by the RNLI within the various study
areas considered in the NRA relating to shipping and navigation.
It was found that no launches to incidents were reported by the RNLI within the Hornsea Three
array area study area with the closest incident approximately 215 m outside of the study area. This
reflects the strategic performance standard of the RNLI of reaching casualties up to a maximum of
100 nm from shore – the RNLI may respond to a drifting vessel but are unlikely to respond to a life-
saving incident in proximity to the Hornsea Three array area owing to the time it would take to get
to the incident from shore.
3 It is noted that construction and operations of Hornsea Three may lead to potential industry incidents requiring SAR response; however this is related to the wind farm rather than the internal layout. All wind farm personnel will be issued with Personal Locator Beacons (PLBs) and will be required to wear these when engaged in activities that present an elevated risk, which should assist the SAR helicopter with pinpointing the casualty.
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Figure 7.3 RNLI incident locations by incident type within 10 nm of Hornsea Three array area
The NRA also considers historical collision and allision incidents involving offshore wind farms.
Research found that there were 13 incidents between 2005 and 2016, as detailed in Table 7.1.
The majority of incidents resulted in minor or moderate damage to the casualty vessel and no
serious injuries were reported. The MCA has indicated that there have been additional incidents
since 2016.
It is noted that the cause of each of the incidents detailed in Table 7.1 was not related to the layout
of the wind farm structures. Causes typically involved negligence by persons, such as misuse of
the auto-pilot. Therefore for these incidents the presence of multiple of lines of orientation would
not have prevented the incident and thus it is anticipated that a SLoO would be sufficient for
minimising the risk of a collision or allision incident.
Table 7.1: Summary of historical collision and allision incidents involving wind farm sites
Project or third party
Incident type Date
Damage to vessel (as per the incident
reports)
Injury to person
Source
Project Allision – service vessel with turbine
7 August 2005 Minor damage to gangway on the vessel
No injury
Maritime Accident Investigation Branch (MAIB)
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Project or third party
Incident type Date
Damage to vessel (as per the incident
reports)
Injury to person
Source
Project Allision – service vessel with turbine
29 September 2006
No damage to vessel
No injury MAIB
Project
Allision – service vessel with disused pile
8 February 2010
Minor damage to vessel
Injury MAIB
Third party and project in harbour
Collision – service vessel with vessel
23 April 2011 Moderate damage to vessel
No injury MAIB
Project Allision – service vessel with turbine
18 November 2011
Major damage to vessel
No injury MAIB
Project
Collision – service vessel with service vessel
2 June 2012 Moderate damage to vessel
No injury
UK Confidential Reporting Programme for Aviation and Maritime (CHIRP)
Project
Allison – service vessel collision with OWF structure
20 October 2012
Minor damage to vessel
No injury MAIB
Project Allision – service vessel with buoy4
21 November 2012
Major damage to vessel
No injury MAIB
Project Allision – service vessel with turbine
21 November 2012
Moderate damage to vessel
Injury MAIB
Project Allision – service vessel with turbine
16 February 2013
Minor damage to vessel
No injury UK CHIRP
4 Previously this incident was listed as being with a turbine but the MCA have provided clarification.
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Project or third party
Incident type Date
Damage to vessel (as per the incident
reports)
Injury to person
Source
Project
Allision – service vessel with turbine
July 2013 Minor damage to vessel
No injury
International Marine Contractors Association (IMCA) Safety Flash
Project Allision – service vessel with turbine
14 August 2014 Minor damage to vessel and pollution
No injury UK CHIRP
Third party Allision – fishing vessel with turbine
26 May 2016 Moderate damage to vessel
Injury Web search (BBC, 2016)
8. Other Evidence
Mitigation Measures – Pre Submission
The NRA includes an extensive list of mitigation measures adopted as part of Hornsea Three,
including both embedded mitigation measures and additional mitigation measures required to bring
specific risks to ALARP. The following list outlines mitigation measures which are relevant to the
case that a SLoO is sufficient for Hornsea Three, noting the NRA assessed a SLoO:
• Charting of Hornsea Three array area – the Hornsea Three array area will be marked on
relevant UKHO Admiralty charts.
• Compliance with UK and Flag State regulations and IMO conventions including COLREGs
and SOLAS – compliance to ensure that standard levels of navigation and vessel safety
continue to be adhered to by all project related vessels during all phases. SOLAS is
discussed in further detail in the next section.
• ERCoP – an ERCoP will be developed and implemented for all phases of the project. The
array layout and SAR Access Lanes (compliant with the Layout Development Principles) will
be included as standard.
• IALA guidance and Aids to Navigation – structures within the wind farm will be marked and lit
in accordance with IALA Recommendation O-139 on the Marking of Man-Made Offshore
Structures (IALA, 2013). Other visual and auditory Aids to Navigation may also be
implemented, and will be placed and characterised in agreement with TH (and MCA) prior to
the start of construction.
• Marine coordination – appropriate marine coordination will be in place to ensure that project
vessels do not present an unacceptable risk to each other or to transiting vessels.
• Other means of communication to assist third parties – use of offshore Very High Frequency
(VHF) aerials, AIS transceivers and the on-site vessels.
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• Shut down procedures – the individual turbines structures will have functions and procedures
in place for generator shut down in emergency situations.
• Promulgation of information – information and warnings will be distributed via Notices to
Mariners and other appropriate media (e.g. Admiralty charts and fishermen’s awareness
charts) to enable vessels to effectively and safely navigate around the Hornsea Three array
area. This may include additional consultation above and beyond the minimum standard
required.
• Self-help capability – provision of self-help capabilities to deal with wind farm associated
emergencies. Consideration shall be given to towage, pollution response and man overboard.
Mitigation Measures – Post Submission
Agreement (as confirmed at the ISH1 on 14th December 2018) has been reached with TH that AIS
transmitters may be fitted to turbines in order to assist with SAR operations. The use of AIS will
provide additional situational awareness to the SAR crew, above and beyond that provided by the
multiple onboard navigation systems and sensors.
The version of the Layout Development Principles published in Volume 4, Annex 3.7: Layout
Development Principles of the Environmental Statement has since been updated following
discussions with the MCA and TH. The Applicant has made concessions from the version included
in the Environmental Statement including:
• Commitment to a Helicopter Refuge Area (HRA) with a width of between 0.5399nm and 1nm
(rather than 1km);
• Tolerance of 100 m either side of the centre line of internal development lanes (rather than
150 m); and
• Tolerance of 50 m either side of the centre line of perimeter development lanes (rather than
150 m).
It is noted that the final SAR Access Lanes will be agreed as part of the Emergency Response
Cooperation Plan (ERCoP). However, as per the Layout Development Principles, Hornsea Three
have committed to SAR Access Lanes which shall:
• Be parallel to turbine development corridors; and
• Satisfy the minimum width of 500 m required by MGN 543 to facilitate SAR Asset access,
where this width is measured tip to tip.
Allow a SAR Asset (at altitudes below 500 feet (ft) to enter the Hornsea Three array area from a
position outside of the Hornsea Three array area (or outside of a phase) and exit the other side of
the Hornsea Three array area (or the other side of a phase) without altering its heading or coming
into close proximity (less than 250 m radius) to any surface infrastructure. With these mitigation
measures in place the navigational risk posed to a vessel navigating within the array is anticipated
to be minimal which further negates the need for multiple lines of orientation.
The Applicant acknowledges that further discussions will be required post consent with the MCA to
finalise the details of mitigation measures such as the ERCoP.
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SOLAS Obligations
Annex 5 of MGN 543 includes the following:
“International practice for SAR response to persons in distress at sea includes alerting and
notifying the nearest vessel(s) (this includes small vessels e.g. fishing vessels and leisure craft) to
an incident location and asking them to render assistance in accordance with the SOLAS
regulations.”
In the case of an incident internally within the array a passing vessel may be obliged to navigate
through the array to render assistance as per SOLAS obligations. In such a case two lines of
orientation may be helpful for larger vessels navigating the array; however there is anticipated to
be a large number of accommodation platforms and vessels on site during operation. As per the
Design Envelope used to inform the NRA, these are as follows:
• Up to three accommodation platforms or up to four Offshore Support Vessels (OSV) which
are likely to carry daughter craft;
• Up to 20 Crew Transfer Vessels (CTV);
• Supply vessels which are likely to carry daughter craft; and
• Marine traffic coordination 24/7.
Given the anticipated vessel support on site throughout the majority of the operation and
maintenance phase, emergency response impacts can be effectively managed. Accounting for the
level of resource on site and the relatively low number of third party vessels in the area (see the
vessel density analysis in section 5), the NRA concluded that it is highly probable that a Hornsea
Three project vessel would be the first responder to render assistance in the event of an
emergency internally within the array. Hence it is considered extremely unlikely that a third-party
vessel would need to enter the Hornsea Three array area under any SOLAS obligation.
Further consultation will take place with the MCA post consent regarding the emergency response
capability of project vessels.
Hornsea Three as a Standalone Development
Annex 5 of MGN 543 includes the following:
“Wind farms which are extended, or adjacent developments which are constructed close to each
other […] All developers involved must undertake to ensure that layouts are harmonised and of the
same general orientation.”
Hornsea Three is not an extension of any existing offshore wind farms. Hornsea Project One and
Hornsea Project Two are located adjacently to Hornsea Three, but these other developments are
separated from Hornsea Three by a navigational corridor of 3.9 nm width and therefore Hornsea
Three should be perceived as a stand-alone array. There are no future developments planned
which would alter this.
Since Hornsea Three is considered a standalone development, there are no existing lines of
orientation which the array is obligated to follow.
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Internal Allision Risk Impact from Navigational Risk Assessment
As well as providing the evidence supporting a SLoO, the NRA also assessed the allision risk for
vessels navigating internally within the Hornsea Three array area. The following subsections
replicate the commentary provided in the NRA and the assessment undertaken in the ES for each
phase of the project. It should be noted that much of the evidence outlined in the preceding
sections is used here. The MCA agreed with the impact assessment presented in the NRA. The
evidence procured since the NRA (in particular the SAR operations work undertaken by Mark
Prior) shows agreement with the NRA’s findings.
Construction and Decommissioning Phases
The presence of infrastructure within the Hornsea Three array area may cause an increase in
allision risk for vessels navigating internally within the Hornsea Three array area; however during
the construction and decommissioning phases measures adopted as part of Hornsea Three will
ensure that the risk is within tolerable limits.
Mitigation measures adopted as part of Hornsea Three include:
• Buoyed construction (or decommissioning) area clearly identifying the location of construction
(or decommissioning) works and vessels;
• For areas where active platform or turbine construction (or decommissioning) activities are
occurring, 500 m safety zones will be in place to protect both construction and third party
vessels. Additionally, 50 m pre-commission safety zones will be used to ensure users are
aware of the risk associated with approaching pre-commissioned turbines;
• A Marine Coordination Centre will fully manage vessels movements associated with Hornsea
Three (although command of each vessel remains with each individual Master); and
• Extensive promulgation of information.
Experience of wind farm construction for developers, contractors and vessel operators is now
extensive, with a number of operational wind farms located within dense shipping areas. Hornsea
Three shall be monitored throughout construction by the Marine Coordination Centre using VHF
and AIS but also through the presence of construction (or decommissioning) vessels. Currently
Hornsea Three is out-with the Global Maritime Distress and Safety System (GMDSS) sea area A1,
but is within sea area A2 meaning that only Medium Frequency (MF) calling or satellite
communications are available with shore (see Figure 8.1).
However MF and satellite communications are not generally carried by recreational vessels or
other smaller vessels due to the high cost of equipment. Therefore, the presence of the Marine
Coordination Centre, offshore VHF aerials, AIS receivers and the presence of on-site construction
vessels (or decommissioning vessels) will provide benefits for communication, monitoring and
SAR. Should a vessel on site require assistance, then Hornsea Three vessels, including under
SOLAS obligations, are beneficially placed to provide information and assets including navigational
information (including weather forecasting) and safety support. This will be discussed further with
the MCA post consent.
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When considering the mitigation measures adopted as part of Hornsea Three, and the positive
effects associated with the presence of the Hornsea Three array area, the risk of allision within the
Hornsea Three array area during construction is assessed to be broadly acceptable (minor
adverse significance in the Environmental Statement).
Figure 8.1: GMDSS sea areas
Operation and Maintenance Phase
Project Vessels
Any vessel and crew present within the Hornsea Three array area during the operation and
maintenance phase shall have a level of competence pre-determined by the Hornsea Three Safety
Management Systems (SMS) and their own Flag State regulations. It is noted that, given the size
of vessels required for the distance offshore of the Hornsea Three array area (65.3 nm), vessels
will typically be larger than previously seen at offshore wind farm developments closer to the coast,
and will be fully certified as per flag state requirements. MGN 280 Small Vessels in Commercial
Use for Sport or Pleasure, Workboats and Pilot Boats – Alternative Construction Standards (MCA,
2004) requires vessels operating over 60 nm from a safe haven to be category one or zero vessels
(scale is six to zero, with six being the lowest level of capability). When considering this in
combination with the level of knowledge the vessel crew will have about the array design, marine
coordination, and the previous low frequency of allision for internal navigation involving project
vessels, the impact are assessed to be ALARP.
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Third Party Vessels
Regular operators were consulted as part of the NRA process and were asked to indicate whether
they would enter the Hornsea Three array area or would navigate around it. Of those that
responded, including during the Hazard Workshop, the majority indicated that they would not
(intentionally) enter the Hornsea Three array area in part due to the small deviations that would be
required in order to avoid it (as part of the entire journey and considering speed reduction they
would likely make to enter the Hornsea Three array area (as with a port entrance channel)). When
considering this alongside lessons learnt from other wind farms where negligible levels of
commercial vessels have been recorded passing through arrays it is considered extremely unlikely
that a commercial vessel would enter the Hornsea Three array area. It is noted that in other
countries (such as the Netherlands) commercial vessels are excluded from entering offshore wind
farms by the regulatory authority.
The SAR guidance annexed to MGN 543 (implemented December 2016) notes SOLAS (IMO,
1974) obligations for third party vessels and the potential need for vessels to enter wind farm array
areas to render assistance. It notes “International practice for SAR response to persons in distress
at sea includes alerting and notifying the nearest vessel(s) (this includes small vessels e.g. fishing
vessels and leisure craft) to an incident location, and asking them to render assistance in
accordance with the SOLAS regulations” (MCA, 2016).
The following list identifies the maximum number of accommodation platforms and vessels on site
during operation:
• Up to three accommodation platforms or up to four OSVs which are likely to carry daughter
craft;
• Up to 20 CTVs;
• Supply vessels which are likely to carry daughter craft; and
• Marine traffic coordination 24/7.
Although not specified within the Design Envelope, based on experience of other offshore wind
farms it is assumed that there will be vessel support on site throughout the majority of the
operation and maintenance phase that will help to ensure that all emergency response impacts
can be effectively managed. Hornsea Three also plan to use helicopters on a regular basis and will
have advanced medical provision on site.
When considering Hornsea Three resources on site against the low number of third party vessels
in the area it is highly probable that Hornsea Three project vessels would be the first to render
assistance in the event of an emergency. It is therefore considered extremely unlikely that a
third-party vessel would need to enter the Hornsea Three array area under any SOLAS
(IMO, 1974) obligation. The risks associated with the requirement for third party vessels being
required to render assistance are therefore considered negligible and ALARP.
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Given the 1,000 m spacing between structures within the Hornsea Three array area, it is assessed
(based on known manoeuvring and expert opinion) that navigational safety within the Hornsea
Three array area will be improved compared to other consented, under-construction, or operational
wind farms. Table 22.1 [omitted – see Table 6.2 above] presents the minimum spacing from
consented wind farms or wind farms that are within the consent process with MCA and TH
approval. It is noted that the minimum internal spacing committed to is significantly larger than
other Round Three developments giving vessels more sea room to navigate and manoeuvre within
the Hornsea Three array area (when considering turning circles and rate of turn).
Experience at an Existing Offshore Wind Farm
London Array offshore wind farm is an example of a wind farm that was consented, constructed
and is currently operational with recreational and fishing activity. It was consented within a busy
and seasonal area for small craft and a specific buoyed navigation channel (Fouglars Gat) was
designed (in the position of an existing preferred route).
Fishing and recreational vessels were identified from AIS data collected between 1 March 2016
and 28 February 2017 (365 days) within the London Array offshore wind farm site boundary.
During this period 140 unique recreational transits were recorded, with only eight vessels not using
Fouglars Gat for the majority of their transit. Of those eight tracks and those that did not fully stay
within Fouglars Gat it was seen that they also do not opt to remain fully within the available straight
lines of orientation.
During the 12 month period only 32 unique fishing vessel transits were recorded within the site
boundary. Of the 49 tracks recorded, 23 broadcast a navigational status of “engaged in fishing”,
with these near the southern boundary; the remaining 26 consisted of passages through the array,
with vessels not, in the majority, following the main lines of orientation.
Similar buoyed channels or additional international Aids to Navigation for use by recreational users
and other small craft could be considered at Hornsea Three in consultation with the MCA, TH and
key recreational users dependant on the final layout selected.
Turbines have the potential to affect vessels under sail when passing through the Hornsea Three
array area from effects such as wind shear, masking and turbulence. From previous studies of
offshore wind farms it was concluded that turbines do reduce wind velocity by an order of 10%
downwind of a turbine (RYA, 2015). The limited spatial extent of the effect is not considered to be
significant, and similar to that experienced when passing a large vessel or close to other large
structures (e.g. bridges) or the coastline. In addition, practical experience to date from RYA
members taking vessels into other offshore wind farm sites indicates that this is not likely to be a
significant issue.
Given mitigation measures adopted as part of Hornsea Three and the potential for additional Aids
to Navigation, the impact on internal navigation is considered tolerable with mitigation
(Development Principles) and ALARP (moderate adverse significance in the Environmental
Statement).
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Increased Internal Allision for Commercial Fishing Vessels and Recreational Craft
Presence of infrastructure within the Hornsea Three array area may increase vessel to structure
allision risk for commercial fishing vessels navigating internally within the turbine array. The
estimated allision frequencies of one every 5.74 years could be considered high when compared to
other allision assessments carried out on developments within UK waters. However the model and
the results reflect the significant maximum surface area assumed for all the structures that could
be developed within the Hornsea Three array area against the medium density of fishing activity.
The fishing allision model assumes that the fishing vessel density following development will
remain the same as current levels; however in reality it is likely both that fishing activity will
decrease and/or fishing vessels will adapt to the layout and continue to fish between the turbines
(as seen at existing operational developments). The model does not assume what type of allision
incident will occur and in reality the most likely would be a minor or low energy impact resulting in
little or no damage to the vessels.
During consultation, the Dutch Fishing Association VISNED also noted that in good weather fishing
vessels are likely to transit through the wind farm. All foundation types including the jacket
foundations considered in the maximum design scenario are assumed to be ALARP based on the
minimum 1,000 m spacing and designed in measures in place to ensure that fishing vessels are
able to safely passage plan transits and activity within the Hornsea Three array area. Further
information is contained within volume 2, chapter 6: Commercial Fisheries.
As with fishing vessels it is considered likely that recreational craft will adapt to navigating within
Layout A given the minimum spacing of 1,000 m; recreational traffic levels are also very low within
the Hornsea Three array area and negligible levels of recreational transits are likely to be seen.
As noted MCA guidance states “that in order to minimise risks to surface vessels and/or SAR
helicopters transiting through an OREI [sic], structures (turbines, substations etc.) should be
aligned and in straight rows or columns” and “the developers (the Applicant) should plan for at
least two lines of orientation unless they can clearly demonstrate that fewer is acceptable” (MCA,
2016).
Following consultation feedback as part of Section 42, the final layout will meet the Development
Principles, including maintaining a single line of orientation, as referenced in section 9.5 [of the
NRA].
Looking at the issue of surface craft navigating within the array, the following factors gathered from
consultation, the Hazard Workshop and marine traffic survey results make the case that Layout A
will be tolerable with mitigation (Development Principles) (moderate adverse significance in
the Environmental Statement):
• Predicted levels of transiting vessels (recreational and commercial fishing) will be low
compared to other constructed and/or consented wind farms;
• While levels of fishing activity are high within some areas of the Hornsea Three array area,
this will vary seasonally and annually. Some commercial fisheries representatives have
indicated that their main concerns are over the foundation type used (minimal snagging risks)
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and minimum spacing rather than the alignment. Overall, the majority of risk associated with
internal navigation is related to vessels engaged in fishing rather than transiting;
• Demersal trawlers active within the array area are expected to target specific fishing grounds,
meaning that it is unlikely that the skippers would choose to fish along fixed lines of
orientation, noting that fishing in the array area has been determined to be low (see
section 5);
• Consultation indicates that commercial vessels (in transit), other than commercial fishing
vessels, will not navigate through the Hornsea Three array area;
• The RYA stated that, given the very low level of recreational traffic within the Hornsea Three
array area, they had no express concerns with the PEIR layouts and did not raise any further
concerns during section 42 consultation;
• With regards to the PEIR layouts the CA confirmed their general policy that wind farms should
have “straight see-through channels between the turbines” while recognising that the Hornsea
Three array is in an area of very light yachting and recreational traffic. The CA confirmed that
the penalty of not having straight see-through “channels” at Hornsea Three “may prove
minimal and therefore acceptable to many” therefore is assumed that the single line of
orientation is a further improvement on random layouts.
• The CA also noted that the penalty of extra time and distance incurred as a result of avoiding
the Hornsea Three array area would mostly be minimal and thus it is likely that yachts and
recreational craft may at the time of passage choose to avoid or be in a position where they
should avoid the Hornsea Three array area;
• The CA stated a preference for additional Aids to Navigation to be provided within the array;
• Marine traffic survey data shows very low recreational vessel movements (especially when
excluding the 500 Mile North Sea Race) and those that were in the area would be well
equipped and experienced (given the distance offshore);
• Aids to Navigation similar to those deployed at the London Array OWF could be used at the
Hornsea Three array area to assist third party internal navigation this however would be
decided by TH post consent;
• Visibility is generally good or very good at the Hornsea Three array area. Appendix C
includes further detail on visibility. The total percentage of time that the visibility is below 2 km
is around 1.3%;
• Cumulatively no other development will border the Hornsea Three array area;
• It is unlikely that third party vessels will be required to perform SOLAS obligations within the
Hornsea Three array area, given that Hornsea Three vessels are likely to be present on site;
and
• The Hornsea Three array area is largely out with the operational area for the RNLI and the
MCA do not operate any surface craft assets within the southern North Sea.
Given that this NRA is only able to consider indicative layouts, the following table identifies
elements that should be considered when assessing site layout post consent, again excluding
consideration for helicopter-based SAR operations. Table 8.1 identifies potential issues identified,
risk ranking for indicative maximum design scenario Layout A and proposed mitigation for layouts
to bring the effects into ALARP parameters. The information presented in Table 8.1 can be used to
inform post-consent layout designs.
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Table 8.1: Effects associated with navigation internally within the Hornsea Three array area
Issue
Receptor and
Frequency of
Receptor
Sources Considered Risk and Proposed
Mitigation
Impact of 1,000 m minimum spacing for all structures on internal navigation
Recreational craft – low frequency user
No negative responses were received by recreational consultees.
One thousand metre spacing would allow recreational craft to manoeuvre between structures given the maximum size of 24 m for recreational vessels (as per the Recreational Craft Regulations 2017 No. 737).
Identification methods for structures currently required by standard guidance were considered sufficient.
No further mitigation associated with minimum spacing required, draft DCO shall state minimum of 1,000 m between all structures.
Impact of 1,000 m minimum spacing for all structures on internal navigation
Commercial fishing vessels – medium frequency over the Hornsea Three array area
Commercial fishing consultees favoured fewer and larger turbines and noted that the separation between turbines is more important than the regularity of the layout.
No further mitigation associated with minimum spacing required, draft DCO shall state minimum of 1,000 m between all structures.
Impact of no maximum spacing for structures on internal navigation
Recreational craft – low frequency user
At greater than 1,000 m spacing recreational craft may not be able to identify low level ID lighting of the next turbine that they are approaching. Therefore additional aids should be considered.
Given the increased spacing and navigational information that will be provided for Hornsea Three, recreational vessels will have greater navigational knowledge, as well as space to sail and manoeuvre.
Based on the shipping template within MGN 543, the turbines will be more visible with fewer echoes on marine Radar systems.
Consultation raised no concerns about maximum spacing.
No further mitigation associated with maximum spacing required, draft DCO shall state no maximum spacing.
Impact of no maximum spacing for structures on internal navigation
Commercial fishing vessels – medium frequency over the Hornsea Three array area
Given the large spacing and increased navigational information that will be provided for Hornsea Three commercial vessels, they will have access to greater knowledge about the site and space to fish and manoeuvre.
Consultation noted that fishing vessels prefer the largest spacing possible.
No further mitigation associated with maximum spacing, required, draft DCO shall state no maximum spacing.
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Issue
Receptor and
Frequency of
Receptor
Sources Considered Risk and Proposed
Mitigation
Impact of exposure to turbines
Recreational craft – low frequency user
Exposure is defined when a vessel is on a transit with turbines on either side of it within a “row” that will then potentially create effects as identified within the shipping template (Radar impacts within 1 nm).
Time spent within the Hornsea Three array area and in proximity to structures will increase risk to vessels. At greater than1,000 m spacing exposure and thus effects will be significantly reduced compared to transits through existing wind farms with smaller spacing.
The greater the spacing and non-alignment of turbines the lower the exposure time.
Impact of exposure to turbines
Commercial fishing vessels – medium frequency user over the Hornsea Three array area
Impact of structure (including turbine) alignment
Recreational craft – Low frequency user
Non-alignment within a row is considered to be a non-grid layout where turbines are converging or diverging.
RYA noted no concerns regarding the misaligned turbines that comprise the PEIR Layouts given the low frequency.
CA noted that they preferred alignment but agreed with the low frequency. The CA section 42 consultation response also notes that increased spacing mitigates some of their concerns over alignment.
Non-alignment can create confusion / disorientation within the Hornsea Three array area. Hornsea Three will provide navigational information via its Marine Coordination Centre to assist.
Stakeholders did not raise any concern between alignment and allision risk.
Given the increased size of other structures (such as substations and accommodation platforms), there are not anticipated to be any impacts from these structures being out of alignment, given that they will provide good Aids to Navigation for surface craft and be visible from a greater distance.
No further mitigation required.
Increased spacing inversely decreases the impact of misalignment.
Recreational vessels are very low frequency within Hornsea Three and therefore the risk of a vessel becoming disorientated (when considering measures adopted as part of Hornsea Three) is negligible.
There is no evidence to suggest that misalignment will directly affect allision risk but that misalignment could cause inconvenience by vessel operators becoming disorientated. Therefore if additional mitigations are in place to aid navigation the change in safety risk is assumed negligible.
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Issue
Receptor and
Frequency of
Receptor
Sources Considered Risk and Proposed
Mitigation
Impact of structure (including turbine) alignment
Commercial fishing vessels – medium frequency over the Hornsea Three array area
Fishing consultation noted that fishing, including trawling and fly-shooting, would be possible in amongst the indicative layouts shown in the PEIR if the weather was suitable and the fish are present.
For fishing, the separation between turbines is more important than the regularity of the layout.
Given the increased size of other structures, there are not anticipated to be any impacts from these structures being out of alignment, given than they will provide good Aids to Navigation for surface craft.
As with recreational craft, increased spacing inversely decreases the impact of misalignment.
Given that Hornsea Project One and Hornsea Project Two do not directly border the Hornsea
Three array area, there are not anticipated to be any impacts with cumulative internal alignment.
9. Other Constraints
Array or wake losses can account for as much as 10% of loss in energy yield within a wind farm,
depending on the proposed layout and wind conditions. The material benefits of optimising layout
are increased efficiency of turbine use and wind capture, maximising the availability of the turbine
array to winds and thus increasing renewable energy production.
While wake losses constitute one of the primary sources of production loss in offshore wind farms,
it is possible to partially mitigate these losses through optimised layout and wind farm design. The
primary mitigation is to increase the distances between turbines in the prevailing wind direction,
thus allowing wake recovery. This mitigation method is not possible to implement to a great degree
in a fixed grid layout. However, a SLoO layout would allow for this mitigation to be implemented.
While the distance between the development lanes would be fixed, as described in the Layout
Development Principles, it is possible to offset the turbines in alternating roles, thus increasing the
distance between two turbines in the prevailing wind direction. This offers the project a way to
optimize electricity production within the parameters set out by the Layout Development Principles.
Detailed geophysical and geotechnical investigations are typically undertaken post financial
decision due to the large costs involved. Ground investigations undertaken for previous projects
have shown that glacial features historically present in this area of the southern North Sea have
led to higher than expected spread and density of boulders (clearing boulders complicates site
preparation and costs). Having the ability to site turbines away from such glacial geological
features mitigates the need to clear wider areas of boulders and thus reduces the extent of
interaction with the seabed.
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10. Summary and Conclusion
This report has considered the content of Volume 5, Annex 7.1: Navigational Risk Assessment of
the Environmental Statement and materials produced in the examination process since the NRA
was submitted in order to provide a justification for the safe implementation of a SLoO for the
Hornsea Three array.
In particular, key points of the safety justification which were discussed in consultation meetings
with the MCA and TH in December 2017 have been considered in detail:
• Vessel traffic levels within the array area are low;
• Minimum spacing and foundation types are a greater concern to fishermen than the lines of
orientation since activity will be dictated by targeted fishing grounds;
• Hornsea Three resources on site are capable of providing an incident response; and
• No other project borders the Hornsea Three array area.
A number of other points supporting the case for a SLoO have been discussed and include the
following:
• Agreement between regular commercial operators in the area that commercial vessels would
not generally use the array area for transiting;
• Large minimum spacing between array structures eases CA concern over irregular layout
patterns5;
• RYA are unconcerned by the number of lines of orientation applied within the array layout
(given the distance from shore and the low level of traffic);
• Vessel traffic density is lower at Hornsea Three compared to the other Hornsea
developments which were both consented with a SLoO;
• Historical AIS data for a large existing array suggests that small craft do not consider the lines
of orientation within the array layout, taking alternative routes instead;
• The Applicant has provided evidence and shared expert helicopter pilot experience during
examination and is of the view that SAR helicopters will be able to turn without risk of a
collision with a turbine in the array area, including in poor visibility;
• The minimum spacing for Hornsea Three is significantly greater than many existing UK
offshore wind farms and gives vessels greater sea room to navigate and manoeuvre within
the array area;
• Historical incident data suggests a collision or allision incident involving Hornsea Three would
not result in major damage to the vessel(s) or serious injury to persons, and any historical
incidents would not be prevented by the inclusion of more than a SLoO;
• Given the distance offshore and the presence of project vessels for Hornsea Three the
likelihood of a SAR helicopter search operation being required are very low;
5 Noting this comment was based on an irregular layout assessed at PEIR and not the SLoO assessed within the application.
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• A suite of mitigation measures will be in place which minimise the risk to a vessel navigating
within the array; and
The number of Hornsea Three vessels anticipated to be on site during operation will be determined
post consent but will be available to respond to safety incidents. Considering this, the likelihood of
a third party vessel being required to enter the array area under SOLAS obligations is low. Based
upon the Layout Development Principles, which the Applicant proposes should be secured by
condition in the DMLs included in the DCO, Hornsea Three commits to:
• Adhering to the guidance contained within MGN 543 (MCA, 2016) with the Layout
Development Principles considered a refinement of the guidance specifically to meet the
requirements of Hornsea Three;
• Locating all s